1. Field of the Invention
This invention relates to apparatus for promoting settling of solids from waste water, and more particularly to a deck and lamina for a settler in which the lamina are light weight and easily removable from the settler, and wherein the lamina may have the angle thereof varied relative to the surface of the waste water while making preset changes to the area of outlets defined by the deck, where the outlets are from flow channels formed by two adjacent lamina.
2. Discussion of Prior Clarifiers
Clarifiers are used to remove certain materials and particles from liquid. These materials are generally suspended in the liquid and can be removed under the force of gravity when the flow of the liquid is substantially reduced, as when there is a very low rate of flow, such as in a quiescent zone (or flow channel) in the clarifier. Since these materials are generally solid and are said to "settle" out of the liquid, they are referred to as "settleable solids". Such settleable solids may include naturally occurring materials (e.g., clay, silt, sand and dirt), chemical precipitants and biological solids. The word "solids" as used herein to describe the present invention refers to such settleable solids.
Clarifiers are used, for example, in water and waste water treatment plants. In water treatment, the water drawn from a water supply has various non-settleable colloidal solids therein. When mixed with chemicals, the colloidal solids and chemicals agglomerate to form settleable solids. In waste water treatment, the solids include organic solids, among other wastes. Water and waste water are treated in clarifiers to remove such solids, thereby making the water clear and suitable for use, reuse, or for further treatment, such as tertiary treatment. The word "liquid" as used herein to describe the present invention refers to water and waste water.
An object of water and waste water clarifiers is to create a low flow rate, such as in flow channels. Low flow rates promote maximum settlement of the settleable solids to the bottom of the clarifiers. Clarifiers typically include a large detention basin where the settlement of the solids occurs. Tubes or flat plates mounted at fixed angles relative to the surface of the liquid have been used to form multiple thin liquid flow channels within the detention basin in an attempt to promote settling of solids in less time using less space. Such plates have been constructed out of relatively heavy, single sheets of metal or plastic that are supported on their sides and connected to the side walls of self-contained modules positioned within detention basins. The liquid containing the solids flows upwardly between the plates or tubes at flow rates that generally allow sufficient time for most of the solids to settle onto the plates or tubes. Ideally, the solids then slide down the plates or tubes to the bottom of the detention basin for collection. Clarified liquid flows out of the openings between and at the top of the plates or tubes.
In some fixed angle lamina settlers, attempts have been made to use thinner lamina. However, in clarifiers such as those shown in Robinsky Patent 4,194,976 issued Mar. 25, 1980, four relatively large vertically extending perimeter members support horizontal dowels which stretch thin lamina sheets and hold them at a fixed angle. The force of a dowel on two of the frame members to which the dowel is attached tends to bend those members toward the opposing frame members, allowing the lamina sheets to sag. Also, the lamina sheets are not easily removable.
Plates of settlers have also been made of flexible, stretchable membranes of synthetic rubber or nylon fabric. Although such membranes are generally light-weight, the supports for such membranes shown in U.S. Pat. No. 4,957,628 to Schulz (issued Sep. 18, 1990) have also been relatively complex and do not allow for rapid removal of individual membranes from the settler. In particular, opposite generally vertical sides of the membranes are hemmed, receive a dowel, and are inserted into upwardly extending tubes provided at opposite sides of the membrane. With the dowel in the hem and the hem in the tube, the tube is secured to an angle adjustment mechanism at the top of the settler. To remove the membrane, the two dowels on opposite sides of the membrane must be removed, which requires handling of the dirty membranes and dowels.
Removal of individual lamina of a settler has been facilitated by (1) resting the bottom of the lamina on a horizontal beam, (2) providing inwardly extending leg portions on fixed angle supports mounted to the side walls of a settler basin to support one of a series of lamina, and (3) supporting other lamina of the series on legs and lugs extending from one lamina into contact with the next adjacent lamina. However, such removable lamina shown in Soriente U.S. Pat. No. 4,889,624 (issued Dec. 26, 1989) are held at a fixed angle relative to the surface of the liquid. The fixed angle does not allow adjustment according to varying settling requirements of the solids. Also in U.S. Pat. No. 4,889,624, horizontally spaced-apart, small-diameter orifices are provided as the sole way in which the liquid exits the top of flow channels formed by adjacent lamina. In addition to the lamina being mounted at a fixed angle, the small-diameter orifices tend to clog much sooner than open-top flow channels, increasing maintenance costs.
Other fixed lamina settlers have been provided. For example, in Heubner U.S. Pat. No. 4,089,782 (issued May 16, 1978); Richard U.S. Pat. No. 4,156,644 (issued May 29, 1979); and Hellman U.S. Pat. No. 4,595,504 (issued Jun. 17, 1986), the upper ends of flow channels of upflow clarifiers are open. Because the lamina are mounted at a fixed angle, these patents do not address flow control problems which might be caused by varying the angle of the lamina.
Troughs have been positioned above the top of such open top lamina. Some troughs have a weir over which clarified liquid flows out of the settler. Other troughs have small holes to admit the clarified liquid as it flows out of the settler. In one embodiment, one such hole is provided for each flow channel. A problem common to such troughs is that the flow of liquid from each flow channel is essentially unregulated, allowing wide variations in the liquid flow rate in different flow channels, and resultant variations from channel to channel in the settling of the solids.
Attempts have been made to provide settlers with lamina that are adjustable. For example, Miura U.S. Pat. No. No. 3,903,000 issued Sep. 25, 1975 mounted lamina for rotation on axes near the top of the lamina. Vibration generators were attached to the lamina and caused a small rotation of the lamina around the axes. The tops of the lamina are above a rod connecting them together. As a result, a plane in which outlets from adjacent lamina are received varies in height with varying angles of the lamina.
Also, U.S. Pat. No. 4,865,753 issued to Applicant on Sep. 12, 1989, hung lamina on brackets, but secured the bottoms of all of the lamina to a ladder-like assembly. Because the ladder-like assembly was in the .liquid to be clarified, one had to drain the liquid from the basin, or enter the liquid, to disassemble the individual lamina from the ladder-like assembly. Also, the upper ends of the lamina were fixed to brackets so that a cantilevered flow controller flap would move only in response to the force of liquid in a flow channel to render the flow in all such channels more uniform. Using the controller flap, as the liquid flow rate and velocity increased, the head loss was constant through an opening defined by the flexed flow controller flaps. However, as the flow controller flaps flex, the separate planes of outlet openings from the settling channels became almost vertical.
Other attempts have been made to provide settlers with lamina that are adjustable. The noted Schulz U.S. Pat. No. 4,957,628 provides a plane defined by the tops of outlets from settling channels. Such plane changes position with changes in the angle of the lamina relative to the surface of the liquid. Such angle is referred to as the "settling angle". Schulz also provides a fixed bottom support member for many lamina, but allows the lamina to pivot on that member as the upper ends of the lamina are moved horizontally to adjust the settling angle. As understood, there is no teaching in Schulz of a relationship between lamina spacing and the area of the outlets at the top of adjacent lamina.